PDS AP Environmental Science 5th Period 2010-11

We just learned about soil degradation through Desertification, Salinization, Waterlogging, and Decreased Fertility.

Desertification is exactly what it sounds like. It is when more fertile land is turned into desert mostly due to drought. Although, human activities such as convention tillage, overgrazing, and salinization contribute to desertification as well. Approximately 30% of crop land and range land is affected. There are various things humans can due to help prevent desertification such as stopping destructive planting and planting “greenbelts” and agroforestry. Agroforestry is the integration of forestry like shrubs and trees into crop land and range land to stop erosion and desertification.

Map of Areas Affected by Desertification

Salinization is when irrigation from farming leaves behind salts. The problem is worse in very arid environments. 70% of cropland is affected. There are solutions to this, but they are extremely complex and expensive. Flushing the soil is when farmers pump in water to the affected area and drain it so that the salts will wash away. The problem with is the water is expensive and needs somewhere to go afterwards.

Salinization of Soil

Waterlogging is when irrigation from farming or soil flushing raises the soil’s water table. If the water table reaches the roots of crops it an lead to root rot(a fungal disease) and lack of oxygen. Around 1/10 of irrigated land is affected.

Finally decreased fertility is when nutrients like nitrogen, potassium, and phosphorus are taken up out of the soil and not replenished. There are many causes for this such as overplanting. Rotating crops is effective in combating this problem. Also organic and inorganic fertilizers are used to replenish soil. The difference between these fertilizers is organic has carbon based nutrients.

Friday in class we learned about human population growth rates. We watched a video. Here is a link to that http://www.youtube.com/watch?v=4BbkQiQyaYc

The world population is around 6.9 billion people right now.

Up to 1800- 1 billion

1938- 2 billion

1960-3

1975-4

1987-5

1999-6

This graph shows the growth in population over time for humans. It is an exponential J curve; however, the growth rate has actually decreased from 2.19% in 1960 to 1.2 in 2010. We are still growing exponentially but the drop shows that we may be close to an inflection point. It took us 15 years to get from 3 billion to 4 then 12 years from 4 to 5, but it took us another 12 to get to 6. Now in 2010 we still don’t have 7 billion people and it has been 11 years.

Then we did population calculations using the rule of 70 to show doubling time. AGR stands for Annual Growth Rate and is always a percent. In this problem we are trying to find out the doubling time for an AGR of 1.5%.

70/AGR(%) =Doubling Time

70/(1.5%)=46.6 years≈47 years

2010+47=2057

We won’t have calculators so you must do long division by hand to show your work.

The is equation determine the AGR or rate of annual increase as it is sometimes called. CBR is crude birth rate and CDR is crude death rate. CBR is births + immigration and CDR is deaths + emigration. Crude just means out of 1000, but you multiply by 100 and 2 zeros cancel. This equation is essential in the next equation because AGR helps calculate population growth per year.

(CBR-CDR)/10=AGR%

(14-9)/10=.5%

The final thing we did was Rate of Annual Increase. THis is when you want to find how much a population has grown or will grow if it is a projection.  I have attached a picture of one way to do it(3APES at the bottom), but I prefer to take the population say 100 and multiply is by the growth rate say 2%. Then add that to the population. 

100*.02=2+100=102

3APES[1]

The biggest problem humans face today is the mass production of meat especially cows. The cows produce more green house gases than all the cars in America, and on top of that the way the cows are treated makes their meat unhealthy to eat. They are pumped full of hormones and antibiotics that are dangerous to people. The problem is growing due to demand for things like fast food.